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How to improve the mounting accuracy of bearings.

wallpapers Resource 2020-05-15

How to improve the mounting accuracy of bearings.

Resource: FAGbearings

Whether the bearing is installed correctly or not affects the accuracy, life and performance. Therefore, the design and assembly department should fully study the installation of bearings. It is expected to be installed according to operating standards. The operating standard items are usually as follows:
(1) clean the bearing and bearing related parts

(2) check the size and finishing of related parts
(3) installation
(4) inspection after installing the bearings
(5) supply lubricant
It is desirable to open the bearing packing shortly before installation. General lubrication grease, do not clean, directly fill the grease, lubricating oil lubrication, general also do not have to clean, but the instrument or high-speed bearings, to clean with clean oil, remove the rust inhibitor coated on the bearings. The bearing that removes antirust agent is easy to rust, so cannot be placed for a long time.

The mounting method of the bearing varies with the structure, fit and condition of the bearing. Generally, the inner ring needs interference fit because most bearings rotate. Cylindrical hole bearing, multi - purpose press in, or multi - purpose hot - loading method. For taper hole, install directly on taper shaft, or install with sleeve.

When installed to the shell, the general clearance fit is more, the outer ring has interference, usually with a press press, or there is also cooling after the installation of the cold shrinkage fit method. Use dry ice as a coolant, shrink to fit the installation occasion, the moisture in the air will condense on the surface of the bearing. Therefore, appropriate anti-rust measures are needed.

(1) Installation of cylindrical bore bearings

Press - in method is widely used for small bearings. Pad the block into the inner ring, press it into the inner ring quietly with the press and close contact with the shaft block shoulder. It is absolutely forbidden to install the inner ring on the outer ring pad, which is the cause of indentation and injury on the roller track.When operating, it is best to oil the mating surface beforehand. If you have to use a hammer to hit the installation, you should put a mat on the inner ring. This practice has repeatedly become the cause of bearing operation, so, limited to the use of small interference, can not be used for large interference, or large bearings. Such as deep groove ball bearings such as non-separation bearings, inner ring, outer ring need interference volume installation occasions, pad pad pad, with screw or oil pressure, the inner ring and outer ring at the same time. Aligning ball bearing outer ring easy to tilt, even if it is not interference fit, it is best to install pad block. Such as cylindrical roller bearings, tapered roller bearings and other separation bearings, can be installed on the inner ring, outer ring on the shaft and shell, will be installed respectively good inner ring and outer ring combined, the key is to firmly close the two, in order to make the center of the two do not produce deviation, reluctant pressure will cause raceway surface card injury.

The method of hot charging Large bearings require a lot of force when they are pressed in, so it is difficult to push in. Therefore, the method of heating the bearing in oil, causing it to expand, and then mounting it onto the shaft is widely used. Using this method, the bearing can be completed in a short time without adding undue force to the bearing. Bearing heating temperature, bearing size, required interference as a reference. Matters needing attention in hot loading operation are as follows: 
(a) do not heat the bearing to more than 120℃;
(b) to keep the bearing away from the bottom of the oil groove, it is advisable to consider placing the bearing on a metal screen or hoisting it up;
(c) heat the bearing to 20 ° c-30 ° c above the required temperature so that the inner ring does not cool during operation, which is difficult to install;

(d) after installation, the bearings cool down and contract in the width direction, so use shaft nuts or other suitable means to tighten them.

(2) Installation of taper bore bearings

Cone hole bearing is directly fixed to the inner ring on the conical shaft, or with a set sleeve, remove the sleeve installed on the cylindrical shaft. Large aligning bearings are multi-purpose oil pressure mounting.

(3) Check operation

After the installation of the bearing, in order to check whether the installation is correct, to carry out operation inspection, small machinery can be manually rotated to confirm whether the rotation is smooth. Check items due to foreign bodies, scars, indentation caused by poor operation, due to poor installation, installation seat processing caused by uneven rotation torque, due to too small clearance, installation error seal friction caused by large torque, etc. If there is no abnormality, power operation can be started.

Since large machinery cannot be manually rotated, the power should be turned off immediately after being started without load to carry out inertial operation. Check whether there is any vibration, sound or contact between rotating parts, etc., and enter into power operation after confirming that there is no abnormality.

Power operation, starting from no load at low speed, and gradually increasing to rated operation under specified conditions. During the test run, the inspection items are, whether there is abnormal sound, bearing temperature transfer, lubricant leakage and discoloration, etc. If any abnormality is found in the test run, the operation should be stopped immediately, and the machinery should be inspected. If necessary, the bearing should be removed for inspection.

Bearing temperature inspection is generally inferred from the outside of the housing. But the use of oil hole, direct measurement of bearing ring temperature, more accurate. The temperature of the bearing starts to rise gradually. If there is no abnormality, it will be stable after 1~2 hours. If the bearing or the installation is not good, the bearing temperature will rise sharply, abnormal high temperature. The reasons include too much lubricant, too small bearing clearance, poor installation, and too much friction on the sealing device. In the case of high-speed rotation, the wrong choice of lubrication method of the bearing is also the reason.

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